Integrated circuits are typically formed from numerous devices packed into small areas of a semiconductor substrate. For the circuitry to function, many of these individual devices need to be electrically isolated from one another. Accordingly, electrical isolation is an integral part of semiconductor device design for preventing the unwanted electrical leaking and coupling between adjacent components and devices.
As the size of integrated circuits is reduced, the devices that make up the circuits must be positioned closer together in order to comply with the limited space available on a typical semiconductor substrate. As the industry strives toward greater density of active components per unit area of a semiconductor substrate, effective isolation between circuits becomes increasingly important. One conventional method of isolating circuit components in modern integrated circuit technology takes the form of trench isolation regions which are etched into semiconductor substrates and filled with insulating material. While device geometries have tended to shrink in the horizontal dimension, electronic devices and isolation trenches in some instances have increased in the vertical dimension. Accordingly, it is a challenge to be able to adequately fill deep and narrow isolation trenches with dielectric material.
One existing technique of filling isolation trenches includes initially filling the trenches with a liquid spin-on-dielectric material, for example a carbon-free polysilazane. These and other spin-on-dielectrics typically deposit to completely fill isolation trenches, thereby resulting in a typically desired void-free filled trench. Unfortunately, many spin-on-dielectrics do not have the desired solidified dielectric properties for the electrical isolating function in the finished circuitry, and/or are not sufficiently dense to adequately resist subsequent selective wet etching of other material(s). Yet, many of the dielectric materials that do have the desired finished dielectric properties cannot be deposited conformally or effective to desirably fill very deep and narrow trenches. Accordingly, one prior art technique of forming trench isolation is to initially deposit a spin-on-dielectric to completely fill deep and narrow isolation trenches over a substrate. Such material is then etched back to leave the lowest portion of the trenches filled with dielectric material and the upper portions outwardly exposed. These upper exposed portions can then be filled with dielectric material having more preferred electrical characteristics.
Unfortunately, the typical etch back of the dielectric material to remove such from the upper portion of the trenches is a timed etch which does not consistently remove the same amount of material from each of the trenches. Thereby, subsequently deposited desired dielectric material is provided in different trenches to different depths and thicknesses which can lead to unpredictable isolation and circuit operation.
While the invention was motivated in addressing the above identified issues, it is in no way so limited. The invention is only limited by the accompanying claims as literally worded, without interpretative or other limiting reference to the specification, and in accordance with the doctrine of equivalents.